Self-locking folding box



Filed Nov. 10, 1948 Nov. 1 l, 1952 R. B. MELLER 7, 80 SELF-LOCKING FOLDING BOX 3 Sheets-Sheet 1 Fi 2 INVENTORY INALD B.MELLER C! at i u, ATTORNEYS Nov. 11, 1952 R. B. MELLER SELF-LOCKING FOLDING BOX 5 Sheets-Sheet 2 Filed Nov. 10-, 1948 Fig 4 INVENTOR. 1 ER I Fig. .5'

REGINALD B. MELL I; A 7' TOR/V1575 Nov. 11, 1952 R. B. MELLER 2,617,580

SELF-LOCKING FOLDING BOX Filed Nov. 10, 1948 s Sheets- Sheet s R E G/NALD .B. MELLER M UM I ATTORNEYS Fig.8

Patented Nov. 11, 1952 UNITED STATES PATENT OFFICE Reginald B.-Mellcr, Oakland, Calif., assignor to Bemiss-Jason. Company, San Francisco, Calif., a corporation of 'California ApplicationNovcmber 10, 1948, Seria1N0;59,328-

, Thisinvention: relates :to-improvements in cartons;boxes,.trays.iandxother structures made from blanks; of cardboard;.i paperboard,- or other "suitable foldable sheet material,v hereinafter. collectively referred to as/boxes." or. folding. boxes.

The: invention. has particular application. to foldingrboxes of the type commonly, although: not quite accurately, called; self; locking. boxes, that is, boxes whichrare maintained: in assembly 3, condition: by" glueless. interen'gagement: of. certain box" elements;

Mostconventional foldingboxesof the so-called self-.lo'cking'type have certain disadvantages or structural limitations which cause the assembled-box to be weaker or less rigid-than a comparable box of glued construction; For example, conventional glueless interlocks are usually sensitive-to certain forces acting onthe boxzwalls from the outside. An'outer: wrapping of cellulose acetate sheet material, for instance, employed for over-wrapping"merchandise-containing trays exerts pressure on. the side walls of the box which pushes .the walls inwardly; thereby tending to disengagethe glueless interlock atthe boxcorner;

Another limitation. of conventional self lockingboxesrests in the difficulty to use covers, particularly hinged covers in boxes of this type. Whereas hinged covers of the tuck type are in wide use on glued boxes because- 0f the simplicity of construction and the ease .with which the cover .can be opened. and reclosed, hinged covers of: the tucktypehave been found difiicult to use on self. locking boxes because ofv the peculiar comer construction of such boxes.

The inventi'onprovides, among other" features,

an-improved interlockfor the formation; without thefuse of adhesives, of a rigid and smooth box corner-free from projections. Ihe box corner-being so constructed that it resists, in a heretofore unattained degree, forces which wouldtend to disengage the interlocking portions of the flaps or panels; More particularly, the invention provides aninterlock which is extremely resistant to forces acting against the walls of the box from the inside and from the outside. The invention further' provides an interlock which is practically freeirom'play or lost motion so "commonly found in construction of .the self. lockingitype'.

. These features make boxes embodying the present invention admirably suitable for tight 13 Claims. (Cl. 229-36) 2 type permitting convenient insertion for flaps or other portions of a. cover or lid..between=.interlocked panelsv or flaps. without danger 'of .Tprying the interengaging portions of the box. apart.

While the invention .is particularly applicable .to the interlocking, of panels at. abox-corner, it..is not limited to such application. but may advantageously be. employedwherever it is desired .to interlock twopanels, or a panel landa flap: ofa folding, box in..a..rigid manner to..produce a con-. nection th'erebetween comparable .in strength. and rigidity to a glued connection, but more convene ient, quicker, and less expensive to. assemble than. a gluedbox.

The interlock. provided. by, the present invention. owes its. strength in no small measure, .to a peculiarity of design which results in the board being subjectedto compression, rather than.tear.- ing, compression being the type-.ofloadwhich the board. isable to sustain most successfully, whereas tear stressis a 1 far. less favorable .form of load.

The invention further providesa form of con.- struction for a hinge eoverbox which is assembled entirely without. adhesive and" may be turned out .on. a.- .small; compact, and. relatively inexpensive machine at a a rate approximately three times-that of a conventionalgluing.machineoccupying. approximately five to tentimes the amount of fioor'spaceandcosting considerably more than. an automatic machine forsetting. up. boxes embodying the present invention.

The various objects, features, and advantages ofathe invention will appear more :fullyfrom. a consideration oftthe detailed description which follows, accompanied by drawings showing, for the purpose of illustration,v preferred embodimentsandapplications. of this invention. 7

Theinvention also consists. incertain. new and improved, details of the construction as hereinafter set forth and claimed.

Although the characteristic features of themvention which are believed to be novel will be particularly pointed out in the claimsappended hereto, theinvention itself,. its objects andv advantages,-and the manner in which. it may be carried out may be better understood by-refe'rring to the followingdescription taken in connection with theaccompanying drawings forming a part of it in which:

Figure l is aplan view of a flat box blank for forming a. hinge cover box with tuck flap closure;

Figure 2-is..a perspective view of the blankof Figure-1 in the process of assembly;

Figure 3 is a perspective view of a box set up from the blank of Figure 1, the cover of the box being nearly closed;

Figure 4 is a perspective view of the box with its tuck flap fully inserted to maintain the cover in closed position;

Figure 5 is a plan view of a blank embodying the invention, the blank being designed to form an open tray or boat having elevated end walls;

Figure 6 is a perspective view of a tray formed from the blank of Figure 5;

Figure '1 is a plan view of a corner portion of a modified blank particularly suited for shallow boxes; and

Figure 8 is a perspective view of a tray formed from the blank of Figure 7.

In the following description and in the claims various structural details will be identified by specific names for convenience. The names, however, are intended to be as generic in their application as the art will permit. Corresponding reference characters refer to corresponding parts in the several figures of the drawings;

In the drawings accompanying, and forming part of the specification, certain specific disclo- 7 sure of the invention is made for the purpose of explanation of broader aspects of the invention, but it is understood that the details may be modified in various respects without departure from the principles of the invention and that the invention may be applied to other structures than the ones shown.

The blank A shown in Figure 1 may be cut and scored in multiple from large sheets or rolls of suitable foldable sheet material, such as paperboard. The blank A is subdivided by several scored fold lines to provide a bottom panel H to which front and back wall panels 12 and 13 are hinged along front and back fold lines 14 and 15. End panels 16 and I1 are hingedly connected to the bottom panel H along end fold lines 18 and 19, respectively. Flaps 20 and 21 are hingedly connected to the end panel l6 along side fold lines 22 and 23. The fold lines 22 and 23 are either in line with, or parallel slightly offset with respect to, the side fold lines 15 and 14 to compensate for the thickness of the board in the succeeding folding operations, as is customary in the art. Flaps 24 and 25 are hingedly connected to the end panel l1 along fold lines 26 and 21 in asimilarmanner as just described. 1 4

A top panel 28 is hingedly connected to the back panel l3 along a top fold line 29, and a tuck flap 30 is hingedly connected to the top panel along a fold line 31. The tuck flap 30 has a main portion 32 of a width substantially equal to the width of the top panel 28, and has a tab portion 33 of reduced width, sufficiently narrow toflt between certain elements of the glueless interlock as will hereinafter be described in greater detail.

The means for interlocking the several panels and flaps of the box comprise internal cuts 34 and 35 in the front wall panel. These internal cuts are preferably of bent outline and form internal tongues 36 and 31 in the front wall panel pointing towards the box corners when the box is considered in set up condition. The internal tongues 36 and 31 may be flexed with respect to the remainder of the front wall panel, and, if so flexed, form wedge-shaped apertures in the front wall panel 12 into which portions of the associated lock flaps 2i and 25 may be moved in the manner whichwill presently be described.

The means-of interlocking further comprise external cuts 38 and 39 extending into the lock flaps 2| and 25 and separating upper flap portions 49 and 4| from lower flap portions 42 and .43. The upper flap portions will also be referred to as being far or remote with respect to the bottom panel II in the set up box, and the lower flap portions 42 and 43 will be referred to as being 'ne'aror close withrespect to bottom panel II. The external cuts 38 and 39 are preferably of bent outline and form tongue shaped flap portions 44 and 45 pointing towards the bottom panel when the box is set up. The external cuts 38 and 39 further form external tongues 45 and 41 on the flaps whose cut edge portions are adapted to engage and interlock with cut edges formed by internal cuts 34 and 35 in the front wall panel. Preferably the interengaging edge portions are in substantial coincidence when the box is set up so as to produce an edge-to-edge engagement possessing far greater strength then a point-to-point engagement of cut edges extending at an angle. This will be described in greater detail in connection with the setting up operation of the box further below.

The external tongues 46 and 41 are preferably so shaped with respect to the outline of the internal cuts 34 and 35 as to extend beyond the outline of theinternal tongues 36 and 31 when the lock flaps and thefront wall panel are in the position which they assume in the finished box. As will later be seen more clearly, tip portions 48 and 49 extend beyond the confines of the internal tongues 36 and 31 particularly portions 59 and 51 of the, internal cuts 34 and-35, when the box panels and flaps are in corner forming position.

The interlock between the back wall panel l3 and the lockflaps 29 and 24 may be somewhat simpler. In the illustrated form of blank it comprises internal cuts 59 and 51 preferably of bent outline, forming internal tongues 52 and 53 in the back wall panel. External cuts 54 and 55 in the lock flaps 29 and 2 4 form external tongues 56 and 51, therein, the tongues being preferably so shaped as to comprise tip portions 58 and 59 .extending beyond the confines of the internal tongues 52 and 53.

The assembly of the blank A into box form may proceed as follows:

The blank A is first folded along the front and back fold lines 14 and 15 to bring the front and the back wall panels into substantially upright position with respect to the bottom panel I I. In

' this position, the stock of the front and the back wall panels is flexed adjacent the internal cuts 34,35, 59, and 51 to deflect the internal tongues 35, 31, 52, and 53 outwardly, thereby opening apertures in the front and back Walls into which the lock flaps 2!, 25, 2!}, and 24 maythereafter be inserted.

The end panels it and H are then folded with respect to the bottom panel 1 I about the end fold lines 18 and I9, and substantially simultaneously the flaps 21, 25, 25, and 24 are folded with respect to the end panels 15 and 11 about their respective fold lines 23, 22, 21, and 26. The lock flaps are brought into parallel position with the upright front and back wall panels 12 and 13 before the end panels 16 and 11 are fully folded into upright position with respect to the bottom panel. Simultaneously the tongue shaped flap portions 44 and 45 of the lock flaps 2| and 25 are flexed towards the inside of the box structure to pass behind the front wall panel 12 as is clearly shown in Figure 2.

The; erection :of the end"panels l9 and I1 is continued while simultaneously the external tongues =46, 56 and 4 1-, 5 of'the flaps are being guided into the open apertures formed bythe defi'e'ction-of the'internal tongues 36,- 52.and 3], 53 lathe-front and 'back wall. This operation brings portions of the external cuts 38, 54, 39, and 55 into-substantial coincidence with portions of the internal'cuts 34," 5B, and '35, 51. In this position, thet'ip portions 48, 58 and 49, 59 0f the-external tonguesstill rest-on the outside of the front and back wall' panel due to the'fact thattheexternal tongues with their tipport'ions extend beyond the contour of the respectiveinternal tongues. The assemblyis completed by pulling the tip portions to the inside of the box so that they overlie the inside surface of the front'and backpanels, respecti vely;

The box corners are now securely interlocked against disengagement. lock-flaps formed bythe--external cuts engage edge portions formedin the front and back wall panels by the internal cuts in edge-to-edge-position-.' Forces-acting against-the end panels l6 and H from the inside of the box, for example pressure exerted 'bythe box contents, are'resisted by. the" interlocks which sustain compressive stress along the interlocked out edges. Compressive stress is safely sustained by the board since the forces act in the plane of the panels, in'which direction the board offers its greatest resistance to-deformation. It will benoted that the tip portions 48, 58, and 49, 59 do not sustain any'part of the load. exertedon the interlock, but merely servesas safety looks, so to speak, for maintainmg the interengaging cut edges inengaging position. In this respect the interlock'forme'd according tothe invention is distinct from, and superior to;glueless"interlocks of'the soecalled hook-type injwhich hook shapedflaps'are subjected to tear.-

Edge portions of the ing,the hook-shaped flaps generally engaging cut edges in'pointato-point relationship.

Pressure exerted against the end walls Hi and I I from the. outside are sustained by the end panels'which rest against the side edges of. the.

front and back panels.

Pressure-exerted. against-the front and back walls 12' and" I3 from the inside of the. box is safely sustained'byth box cornerconstruction by reason of thereinforcement aiforded 'by the lock ;flaps.29', 21, 24, andZS which overlie. the front. and the back walls:

Forces acting on the front wall from the outside: of the box are resisted primarily by the tongue shaped flap portions 64 andi whichlie onthe inside-of the front.wall'.panel..,l2 and prevent caving in of the front. wall panel which, as iseaslly-seen, would tend to.di'sengage the interlooking out. edges at the cornersof the front wall. The back wall is sufficiently secure against such caving in by the presence of the hinged-.cover held in carton closing position by frictional eneasement making it easy to open and reclose the box.

The. improved interlock provided by the inven- 6. tlon particularly suited for open. trays which after filling iwith merchandise arezoverw-rapped. generally witha sheet of' transparent material such as cellulose acetate.

Atypical blank for such a tray isishown-in Figure 5.

The blank B comprises a bottom panel 60 having' side wall panels BI and 62 connectedto it along bottom; fold lines 63 and 64. End wall panels '65 and GB'are hingedly connected to the b'ottompanel 681 along end fold lines 61 and, respectively; Lock flaps B9 and HI are-hingedly connected to the end panel 65. along side'fold lines H and 12. Similar box. flaps 13 and 14 are hingedly connected to the end panel 66" along sidefold lines 15 and; 16. The side:fold lines 1|, 15 and the side fold lines 12, 16 maylie in line with. the bottom fold lines 63 and. 64 or. as'

shown; in Figure 5, may be ofi'set slightlyto compensate for thethickness of the. board.

Internal cuts TI, l8; l9; and '80 form internal tongues 8|, 82, 83, and 84 in the side wall panels which upon flexing with respect to the remainderof the side wall panels open apertures intowhich portions of the lock flaps 69, 10, 73 and 14 may be inserted.

The lock flaps are partially severed by external cuts 85, 86, 87, and 88- and are divided into far portions 90, 9|, 92, and 93 remote-with respect to the bottom panel, and near portions 94, 95, 96 and 9-! closeto the bottom panel. The near: flap portions 94; 95, 95,..and 9-! constitute external tongues and are provided; sirnilarto blank A, with. tip portions 98, 99, I00, and" NH extending beyond the confines of. the. respective in the same manner as hereinbefore.described in connection with the assembly of the .boxillustrated in..Figures -1 to 4. Briefly, the side wall panels GI and 62 arefolded into upright position with. respect to the bottom panel'fifl. The end panels fidand. 66 are then folded. about their respective .fold lines and the flaps 69,..10, 13, and 14 are folded with respect. to the end panels to assume a position parallel to the erected side walls BI and 62. The external. tongues 94,

95, 96, ands! are inserted into the apertures formed in the side walls GI and: 62 byoutward flexing of the internal tongues 8!, 82, 83,. and

84. Simultaneously the downwardly extending flap. portions 90, Si, 92, and 93 are .flexed inwardly to move behind the side wall panelsil and 52. After the end walls and the. four corner or look flaps have reached their final position, portions of the edges formed by the external cuts in the flaps engage portions of the edges formed by the internal cuts in the side walls. in edge-to-edge postion as in the case of blank 'A.

As afinal operation the tip portions 98;v 99, I00, and It! are pulled towards the inside of the box to maintain the interlocking edges in engaging position. However, it should be noted, that even without such tip portions the stiffness of the board tends to maintain. the edges engaged due to a further peculiarity of the presentinterlock. As is apparent from the drawing, the'internal and the external tongue at. each .ofi'ers little resistance to deflection;

corner are oppositely directed, so that the root portion of one tongue where the tongue ofiers great resistance to flexing lies adjacent .the tip portion of the other tongue where the latter similarly the root portion of the other tongue lies adjacent the tip portion of the one tongue where the latter offers the least resistance to flexing and is thereby flexed into engaging position. In other words, the stifiness of the board is taken advantage of and the construction is such that each tongue tends to maintain the other in engaging position, rather than tending to push it out of engagement.

The set up box or tray is shown in Figure 6 and is ready for filling, and overwrapping, if desired.

A box which may either be considered an open tray, a box body, or a telescoping cover for a separate box body is shown in Figure 8. It is set up from a blank C of which, for the reason of simplification, only a corner portion is shown in Figure 7.

The blank C comprises a main panel I02 which may either be the bottom or the top of the resulting box structure, depending on whether it is to be used as the body or the cover of the box. A side wall panel I03 is hingedly connected to the main panel along a side fold line I04. An

end panel I05 of qual height as the side wall panel l03 is hingedly connected to the main panel along an end fold line I06. A flap I! is hingedly connected to the end panel I along a fold line I08 which may be parallel and slightly offset with respect to the side fold line I04 to compensate for the thickness of the board as set forth in connection with the previously described blanks A and B.

An internal cut I09 forms a resiliently deflectable internal tongue H0 in the side wall panel I03 which, upon deflection with respect to the remainder of the side wall panel, permits insertion of a portion of a flap I01 into the resulting slit or aperture.

The lock flap I01 is severed by an external cut III of bent outline into a far portion H2- and a near portion H3. The near flap portion constitutes an external tongue and is provided, similar to blank B, with a tip portion [14 extending beyond the confines of the internal tongue H0 when the flap I0'I is folded into corner forming position with respect to the side wall panel I03.

The far portion I I2 constitutes a tongue pointing towards the main panel. This tongue is designed. to overlie the inside surface of the side wall panel I03 when the box is set up. The corner of the side wall panel I03 is cut away attion of the assembly procedure may for thisrea' son be dispensed with.

A comparison of the form of the external cuts in the flaps of blanks A, B, and C shows that the contour of this cut may be varied considerably. In blanks A and B the inner branch of the external cut is nearly vertical and the outer branch extends at an angle thereto, considering the assembled box. In the blank 0 the V-shape of the external cut is nearlysymmetrical and the inner arm of the cut extends atan angleless than 45. degrees with respect to the horizontal. The angle of the inner arm of the external cut is, therefore, a matter of choice and may be se-.

lected for each particular box according to the specific requirements.

The invention thus provides an improved form of glueless interlock which produces an extremely rigid box corner resistant to deformation by forces acting on the box walls from the inside as well as from the outside. In addition to lending a high degree of rigidity to the glueless interlock the portions of the blank hereinbefore referred to as tongue shaped flap portions 44, 45; 90, 9|, 92, 92; and H2 protect the external locking tongues against damage or accidental disengagement during filling of the box. This feature is particularly well apparent from Figures 6 and 8. Referring to Figures 6, it will be seen that the tongue 92 prevents box contents inserted into the box from catching, damaging, or deflecting the tip portion I00. Similarly, in

Figure 8 the far flap portion II 2 protects the lockingportion II3 by forming a substantially smooth inner box surface therewith at the corner.

The novel interlock has the advantage that it can be handled on automatic high speed machines of small size and relatively simple construction.

As the illustrated forms of boxes show, the invention is equally adaptable to boxes with and without covers.

Obviously the present invention is not restricted'to the specific embodiments herein shown and described, but may be applied with equal benefit to other forms of boxes. Numerous additions, omissions, substitutions and other changes may therefore be made in adapting the invention to specific needs without departure from the spirit and the essence of the invention.

What is claimed is:

1. An improved glueless corner construction for folding boxes for assembling in corner form ing relationship, a main panel, two wall panels hinged to the main panel along fold lines forming an angle, and a flap hinged to one of the wall panels along the side of said one wall panel, the flap being adapted to lie face-to-face with said other wall panel when the panels are in corner forming position, the 'corner construction. being characterized by an interlock comprising, an internal cut of bent outline in said other wall panel forming an internal tongue in said other wall, panel pointing towards the box corner when the panels are in corner forming position, the internal tongue, upon flexing with respect to the remainder of said other wall panel, forming a wedge shaped opening in said other wall panel into which a portion of said flap may be swung, said flap having an external cut of bent outline extending into it from an outer edge, said external cut separating an upper flap portion from a lower flap portion, each of said flap portions being bordered by said external cut and at least one outer edge of said flap, said lower flap portion being insertable, at least in part, into said wedge shaped opening through said internal cut, thus underlying said internal tongue but overlying said other wall panel beyond the confines of said other wall panel as the lower portion is being: swung into said opening, the internal cut and. the external cut providing out edges in said other wall. panel and on the lower flap portion, respectively, which, in the position in which said other panel and flap are to be interlocked are insubstantial line-to-line coincidence permitting an edge portion of one cut to engage an edge portion of the other out in edge-to-edge position, the internal tongue and said lower flap portion." pointing in opposite directions and deflecting each other into edge-to-edge engagement of said cuts, whereby the inherent stiffness of the stock is utilized in assisting the respective edges automatic-ally to move into engagement and remain in engaged position, said upper flap portion reinforcing the interlock against disengagement by forces acting on said other wall panel from the inside or outside.

2. An improved glueless corner construction for folding boxes for assembling, in corner forming relationship, a main panel, two wall panels hinged to the main panel along fold lines forming an angle, and a fiap hinged to one of the wall panels along the side of said one wall panel, the flap being adapted to lie face-to-face with said other wall panel when the panels are in corner forming position, the corner construction being characterized by an interlock comprising, an internal out of bent outline in said other wall panel forming an internal, tongue in said other wall panel pointing towards the box corner when the panels'are in corner forming position, the internal tongue, upon flexing with'respect to the remainder of said other wall panel, forming a wedge shaped opening in said other wall panel into which a portion of said flap may be swung, said flap having an external cut of bent outline extending into it from an outer edge, said external cut separating an upper tongue shaped flap-portion from a lower flap portion, said upper tongue shaped flap portion pointing towards the main panel when the panels and flap are in corner forming position, each of said flap portions being bordered bysaid external cut and at least one outer edge of said flap, said lowerflap portion being insertable, at least in part, into said wedge-shaped opening through said internal cut, thus underlying said internal tongue but overlying said other wall panel beyond the confines of saidinternaltongue, said upper flapporti'on being. movable to lie face-to-face with the inside of said other'wall' panel as the lower portion is being swung into said opening, the internal cut and the external cut providing out edges in said other wall panel and on the lower flap por-- tion respectively, which, in the portion in which said other panel and flap are to be interlocked are in a position to engage each other, the internal tongue and said lower flap portion pointing in opposite directions and deflecting each other into" engaging position, whereby the" inherent stiffness flap being adapted to lie face to-fac'e with said other wall panel when the panels are in corner forming position, the corner construction being characterized by an interlock comprising, an internal cut of bent outline in said other wall panel forming an internal tongue in said other w'all panel pointing towards the box corner when the panels are in corner forming position, the internal tongue upon flexing with respect to the remainder of said other wall panel, forming a wedge shaped opening in said other wall panel into which a portion of said flap may be swung, said flap having an external cut of bent outline extending into it from an outer edge, said external cut separating an upper flap portion from a lower flap portion, each of said flap portions being bordered by saidexternal cut and at least one outer edge of said flap, said lower flap portion being insertable, at least in part, into said wedge shaped opening through said internal cut, thus underlying said internal tongue but over lying said other wall panel beyond said internal tongue, said lower flap portion having a tip thereon extending beyond the confines of the internal tongue when the panels are in corner forming position, the tip being forceable, against the resistance of the stock from which the box blank is formed, from an overlying position with respect to said other wall panel through said internal c'ut into a position underlying said other wall panel, said upper flap portion being movable to lie faceto-face with the inside of said other wall panel as the lower portion is being swung into said opening, the internal cut and the external cutproviding cut edges in said other wall panel and on said lower flap portion, respectively, which, in the position in which said other panel and flap are to be interlocked are, except for said tip, in substantial line-to-line coincidence permitting an edge portion of one cut to engage an edge portion of the other out in edge-to-edge position, the internal tongue and said lower flap portion pointing in opposite directions and deflectingeach other into edge-to-edge engagement of said cut's, said tip, when forced into a position underlying said other wall panel, locking said other panel and said flap in engaging position, and said upper flap portion reinforcing the interlock against disengagement by forces acting on said other wall panel from the inside or outside.

4. An improved glueless corner construction for-folding boxes forv assembling, in corner form'- ing relationship, a main panel, two wall panels hi'ngedzto the main panel along fold lines for-ining an angle, and a flap hinged to one ofthe wall panels along the side of said one wall panel, the flap being adapted to lie face-to-fac'e withsaid other wall panel when the panels are in corner forming position, the corner construction being characterized by an interlock comprising, an in ternal cut of bent outline in said other wall panel forming an internal tongue in said other wall panel pointing towards the box corner when the panels are in corner forming position, the internal tongue, upon flexing with respect to the remainder of said other wall panel, forming a wedge shaped opening in said other wall panel into which a portion of said flap may be swung,- said flap having anexternal cut of bent outline extending into it from an outer edge, sneer ternal cut separating an upper tongue shaped flap portion from a lower fiap'portion, said upper tongue'shapedfiap portion pointing towards the main-panel when thepanels and flap are in corner forming position, each of said flap'por'ti'ons being bordered 'by said: external out and at least one out-er edge of said flap,- said lower flap portion 11 being insertable, at least in part, into said wedge shaped opening through said internal cut, thus underlying said internal tongue, but overlying said other wall panel beyond said internal tongue,

said lower flap portion having a tip thereon extending beyond, the confines of the internal tongue when the panels are in corner forming position, the tip being forceable, against the re sistance of the stock from which the'box blank is formed, from an overlying position with respect to said other wall panel through said internal cut into a position underlying said other wall panel, said upper flap portion being movable into a position face-to-face with the inside of said wall panel as the lower portion is being moved into said opening, the internal cut and the external cut providing cut edges in said other wall panel and on said lower flap portion, respectively, which, in the position in which the said other panel and said flaps are to be interlocked are, except for said tip, in a position to engage each other, the internal tongue and said lower flap portion pointing in opposite directions and deflecting each other into engaging position, said tip, when forced into a position underlying said other wall panel, locking said other panel and said flap in engaging position, and said upper flap portion reinforcing the interlock against disengagement by forces acting on said other wall panel from the inside or outside.

5. A folding box made from a sheet of foldable stock and comprising a main panel; a first wall panel hingedly connected to the main panel along a first fold line; a second wall panel hingedly connected to said main panel along a second fold line extending at an angle with respect to said first fold line, said panels being foldable about said fold lines with respect to one another into a position in which they form a box corner; and a lock flap hingedly connected to one of said wall panels and foldable with respect thereto into a position overlying the outside surface of the other wall panel when the panels are in corner forming position, the said other wall panel having an internal cut therein, said lock'fiap being divided by a' cut into a portion far with respect to the main panel, and a portion near with respect to the main .panel, the far portion underlying the inside surface of said other wall panel, the near portion extending through said internal cut in said other 7 wall panel, at least a portion of said internal out being insubstantial line-to-line coincidence with a portion of an edge formed by said external cut on said near portion of the flap to interlock with said last named edge portion when said panels are in comer forming position, said far portion being free from edge-to-edge engagement with said internal cut, but having an edge aligning with said portion of line-to-line engagement in box forming position, thereby exerting outward pressure on said wall panel at said portion of engagement tending to flex the wall panel into the plane of theengaging near portion.

6. A folding box made from a sheet of foldable stock and comprising a main panel; a first wall panel hingedly connected to the main panel along a first fold line; a second wall panel hingedly connected to said main panel along a second fold line extending at an angle with respect to said first fold .line, said panels being foldable about said fold lines with respect to one another into a position in which they form a box corner; and a lock flap hingedly connected to one of said wall panels and foldable with respect thereto into a position overlying the outside surface of the other wall said one wall panel, said lock flap being divided by a cut into a portion far with respect'to the main panel and a portion near with respect to the main panel, the far portion underlying the inside surface of said other wall panel, the near portion extending through said internal cut in said other wall panel, at least a portion of said internal out being in substantial line-to-line coincidence with a portion of an edge formed by said external cut on said near portion of the flap to engage in edge-to-edge relationship the said edge of the near flap portion when the panels and flap are in corner forming position, the engaging edge portions extending transverse with respect to an imaginary circle crossing the said engaging edge portions and having the fold line of said one wall panel as a center, if the corner is viewed in side view, in which case the last named fold line appears as a point.

'7. The structure as set forth in claim 6 in which the near flap portion is so shaped with respect to the said internal cut as to extend with a tip portion beyond the confines of said internal tongue, the tip being forceable, against the resistance of the stock from which it is formed from an overlying position with respect to said other wall panel through said internal cut into a position underlying said other wall panel to secure said flap and said other panel against separation of their engaging edges.

8. A folding box made from a sheet of foldable stock and comprising a main panel; a first wall panel hingedly connected to the main panel along a first fold line; a second wall panel hingedly connected to said main panel along a second fold line extending at an angle with respect to said first fold line, said panels being foldable about said fold lines with respect to one another into a position in, which they form a box corner; and a lock flap hingedly connected to one of said wall panels and foldable with respect theretointo a position overlying the outside surface of the other wall panel when the panels are in corner forming position, the said other wall panel having an internal cut of bent outline therein forming an internal tongue in said other wall panel pointing towards said one wall panel, said lock flap being divided by an external cut of bent outline extending into it, into a portion far with respect to the main panel and a portion near with respect to the main panel, the far portion forming a tongue pointing towards the main panel and underlying the inside surface of the. said other wall panel, the near portion forming an external tongue oppositely directed with respect to said internal tongue, said external tongue extending through said internal cut in the other wall panel to underlie, at least partially, said internal tongue, an edge portion formed on said external tongue by said external out being in substantial line-to-line coincidence with an edge portion formed in said other wall panel by said internal cut in the position in which the panels and flap are in corner forming position, I the internal tongue bearing down upon said external tongue and flexing it into edge-to-edge engagement of said coinciding edges.

9. The structure as set forth in claim 8 in which the near flap portion is so shaped with respect to the said internal cut as to extend with a tip portion beyond the confines of said internal tongue, the tip being forceable, against the resistance of the stock from which it is formed from an overlying position with respect to said other wall panel through said internal cut into a position underlying said other wall panel to secure said fiap and said other wall panel against separation of their engaging edges.

10. The structure as set forth in claim 8 in which the corner of said other wall panel is cut away adjacent said one wall panel, and in which the inner end of the external cut in the said flap rests in the cut away portion of said other wall panel.

11. A folding box made from a sheet of foldable stock and comprising a bottom panel; front and back wall panels hingedly connected to the bottom panel along front and back fold lines; side wall panels hingedly connected to the bottom panel along side fold lines; a top panel hingedly connected to the back panel along a top fold line; a tuck flap hingedly connected to the top panel along a fold line and lock fiaps hingedly connected to the side wall panels and foldable with respect thereto into a position overlying the outside surface of the front wall panel when the box is set up, said lock flaps being interlocked with said front wall panel, each of the interlocks including an internal cut of bent outline in said front wall panel forming an internal tongue in said front wall panel pointing towards the respective side wall, said lock flap being divided by a cut into a portion far with respect to the bottom panel, the far portion underlying the inside surface of the front wall, the near portion extending through the respective internal cut in the front wall panel, at least a portion of said internal out being in substantial lineto-line coincidence with a portion of an edge formed on said near portion of the respective flap by said external cut to engage in edge-to-edge relationship the said edge of the near flap portion when the box is set up, the end of the tuck flap being reduced in width sufficiently to fit behind the front panel and frictionally seat between the back surface of the front panel and the front surface of the far flap portions lying in back of the front panel.

12. The structure as set forth in claim 11 in which the near flap portions are so shaped with respect to the internal cuts as to extend with a tip beyond the confines of the respective internal tongues, the tip being forceable against the resistance of the stock from an overlying position with respect to the front wall panel through the internal cut into a position underlying the front wall panel.

13. A folding box made from a sheet of foldable stock and comprising a bottom panel; front and ham: wall panels hingedly connected to the bottom panel along front and back fold lines; side wall panels hingedly connected to the bottom panel along side fold lines; a top panel hingedly connected to the back panel along a top fold line; a tuck flap hingedly connected to the top panel along a fold line; and lock flaps hingedly connected to the side wall panels and foldable with respect thereto into a position overlying the outside surface of the front wall panel when the box is set up, said lock flaps being interlocked with said front wall panel, each of the interlocks including an internal cut of bent outline in said front wall panel forming an internal tongue in said front wall panel pointing towards the respective side wall, said lock fiap being divided by an external out of bent outline extending into it into a portion far with respect to the bottom panel, and a portion near with respect to the bottom panel, the far portion forming a tongue pointing towards the bottom panel and underlying the inside surface of the front wall, the near portion forming an external tongue, the external tongue extending through said internal out in the front wall panel to underlie, at least partially, said internal tongue, an edge portion formed on the said external tongue by said external out being in substantial line-to-line coincidence with a portion of said internal out to engage in edge-to-edge relationship the front wall panel at said internal cut portion when the box is set up, said external tongue having a tip extending beyond the confines of the internal tongue, the tip being forceable against the resistance of the stock from an overlying position with respect to the front wall panel through the internal cut into a position underlying the front Wall panel to maintain said edge portions in edge-to-edge interengaging position, the end of the tuck flap being reduced in width sufficiently to fit behind the front panel and frictionally seat between the back surface of the front panel and the front surface of the far flap portions lying in back of the front panel. REGINALD B. MELLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 691,458 Ferres Jan. 21, 1902 1,559,242 Fox Oct. 27, 1925 2,303,796 Rueckert Dec. 1, 1942 2,304,362 Huye Dec. 8, 1942 2,366,419 Meller Jan. 2, 1945 2,419,391 Crary Apr. 22, 1947 2,475,279 Dunning July 5, 1949 2,488,706 Buttery Nov. 22, 1949 

